Antiphospholipid syndrome is an autoimmune disorder characterized by a hypercoagulable state, leading to arterial and venous thrombosis. We present a 23-year-old patient, suspected of having Budd-Chiari syndrome due to antiphospholipid syndrome, who developed severe and progressive hypoxemia, requiring prolonged mechanical ventilation. After a detailed but unsuccessful workup, a contrast CT scan revealed an occluded superior vena cava and azygos vein-superior vena cava junction and massive right-to-left shunting through a network of systemic to pulmonary venous collaterals. Restoring normal blood flow from the azygos vein into the right atrium by stenting the azygos-superior vena cava junction resolved the hypoxemia immediately. Within the same procedure, the hepatic outflow obstruction was successfully treated by stenting a severe stenosis of the suprahepatic inferior vena cava caused by calcified thrombus.